Property or method "previewUrl" is not defined on the instance but referenced during render. Make sure that this property is reactive, either in the data option, or for class-based components,

Property or method "previewUrl" is not defined on the instance but referenced during render. Make sure that this property is reactive, either in the data option, or for class-based components, by initializing the property.

报错原因：视图中上使用了该变量（previewUrl），但初始化时没有定义该变量！

 <img class="" :src="previewUrl" alt="">

export default {

　　name:'index',

　　data(){

        　　return {

       　　　　previewUrl：" ", //定义后即可解决

　　 　　}

　　}

}